Hey,
At the moment for toast show on Shopify POS we can only provide the content, we can’t change the colour or duration of it.
I’ve had feedback from merchants that this makes it hard to catch the difference between errors and notifications and also hard to read.
Please could these be considered as options, like we have in Shopify Admin please 
to this, being able to change the duration is fairly important to give merchants time to read the longer messages, ideally we’d have the option to make it infinite and dismissible instead too.